This invention relates to a cementing collar for use in a string of well liner and actuating means for opening and closing ports in the collar. In particular, this invention is directed to such a collar for use in multiple stage cementing operations of oil and gas wells with the actuating means adapted to be moved down the well casing after performing the actuating functions, thereby eliminating the need for subsequently drilling or milling through these means.
In the drilling and completion of oil or gas wells, it is often desirable to cement a well pipe or casing into the well bore and this is conventionally accomplished by pumping cement slurry down through the casing and out into the annular space between the well bore and the casing. The cement slurry is introduced into the annulus at or near the bottom of the well casing, but if the casing is extremely long or the annulus is small the cement bond and fill at the upper or medium portions of the casing may not be entirely satisfactory. Moreover, occasionally it is highly desirable to obtain a particularly good cement fill and bond in the annulus at a selected upper or medium portion of the casing as well as near the bottom thereof. Thus, it has become customary under these conditions and requirements to perform multiple stage cementing where cement slurry is introduced into the annulus between the casing and the well bore in successive stages at more than one location along the length of the casing.
There are a number of devices known as "cementers" or "cementing collars" which may be used for introducing the cement slurry into the annulus from within the well casing at a particular intermediate point along a well casing. These cementing collars are interposed in the string of the well casing and have normally closed ports which may be opened for permitting the discharge of cement slurry into the annulus and then permanently closed. These opening and closing steps are generally accomplished by dropping or pumping a pair of plugs, bombs or other devices down the well casing to actuate components of the cementing collar. The first device engages a portion of the cementing collar and opens the ports and the second device engages another portion of the cementing collar and closes the ports. These devices are retained in conventional cementing collar and if it is subsequently desired to gain access to the casing below the cementing collar, it is first necessary to drill through these retained devices. Since the particular operation which is to be performed below the cementing collar does not always permit the provision of a drill on the end of a string of pipe being lowered into the casing to perform such operation, this drilling must be conducted as a separate preliminary operation requiring a time-consuming round trip with a drill and string of pipe.
When pumping cement slurry down the casing for these cementing operations, it is conventional and practical to drop a plug into the casing below the cement slurry to open the ports and drop a second plug into the casing on top of the cement slurry to close the ports; these plugs are commonly referred to as "bottom" and "top" plugs, respectively. When multiple stage cementing is carried on the cementing collar must have a large enough minimum internal diameter to permit the top and bottom plugs used in the cementing stages carried on below that collar to pass through the collar without actuating the collar. It is highly desirable that the cementing collar have a minimum internal diameter approximately equal to the internal diameter of the casing both before and after the cementing stage is carried on through that collar so that other tools and devices may be lowered through the collar without the collar presenting any greater obstruction than the casing itself. U.S. Pat. No. 3,768,556 issued to Eugene E. Baker and assigned to Halliburton Company, Duncan, Okla. discloses typical cementing tools currently used in multistage cementing operations. Additionally, U.S. Pat. No. 3,228,473, also issued to Eugene E. Baker and assigned Halliburton Company, Duncan, Okla. discloses a cementing collar and means for actuating the same and is a further typical representation of cementing collars. Other patents showing conventional cementing collars would include U.S. Pat. No. 3,789,926, issued to Ronald W. Henley, et al.; U.S. Pat. No. 2,998,075, issued to Earnest H. Clark, Jr., assigned to Baker Oil Tools, Inc., Los Angeles, Calif.; U.S. Pat. No. 2,925,865, issued to Owen and Oliver, assigned to Halliburton Company, Duncan, Okla.; U.S. Pat. No. 3,527,297, issued to William L. Todd, assigned to Jerry L. Pinkard and U.S. Pat. No. 3,338,311, issued to Martin B. Conrad.
It is noted that the above referenced patents, and others, employ the use of shear pins and/or spring actuated contacting means for causing ports located on an inner sleeve to become radially aligned with ports located on an outer sleeve in order to permit the cement slurry to flow outwardly through the radially aligned ports and thereafter up the annulus between the casing and the well bore. Conventionally, the bottom plug as it is dropped through the well casing, contacts the shear pins and/or spring actuators and causes them to be dislodged and upon the application of hydraulic pressure upon the cementing slurry located immediately above the bottom plug the ports become radially aligned.
However, the use of such shear pins and/or spring actuators does not permit the testing of cementing collars utilizing the same without destroying the functional utility of the cementing collar itself. Additionally, such shear pins and/or spring actuators may be subject to premature actuation when in place in a well string and accordingly may hinder the entire drilling operation.